Polylactic acid (PLA), a renewable resource mainly obtained from corn starch and sugar cane, is one of the most important bio-based and biodegradable plastics, and may replace petroleum based plastics in a range of applications. For the production of PLA, lactic acid (LA) is typically first converted into lactide (LD), its cyclic dimer. Subsequently, this lactide is converted via ring opening polymerization into PLA. However, the most costly step is the conversion of lactic acid into lactide.
Currently, industrial lactide synthesis occurs mainly through a two-step process. A first step in the two-step process is the synthesis of a low quality lactic acid polymer. A second step is the conversion of this polymer into lactide via depolymerization, i.e. backbiting. This two-step process is typically energy consuming, selectivity is low, and significant amounts of meso-lactide, an undesired lactide, are generated. Alternatively, lactide may be synthesized in a gas-phase process over packed solid catalyst beds. Though cheaper than the two-step process, this industrial process has limited yield and/or limited volumetric productivity.